The Bypass Angioplasty Revascularization Investigation (BARI) is a randomized international multicenter trial that compares a strategy of initial percutaneous transluminal coronary angioplasty (PTCA) to that of initial coronary artery bypass graft (CABG) surgery. The ancillary lipid study utilizes a cohort of the BARI participants to examine issues related to lipid management. Previous studies have demonstrated that the treatment of hypercholesterolemia reduces the risk of cardiovascular events and perhaps retards the progression of coronary disease. However, the influence of "normal" plasma cholesterol levels (as defined by the expert panel of the National Cholesterol Education Program) on the progression and regression of coronary atherosclerosis has not been described. Several clinical studies have shown that plasma concentration of apolipoproteins provides a better means of discriminating between patients with and without coronary disease than do the levels of lipoproteins. Following revascularization with coronary bypass surgery, it has been shown that graft stenoses are associated with hyperlipidemia and that treatment of hypercholesterolemia reduces the incidence of graft lesions. In addition, apoproteins as well as triglyceride-rich lipoproteins have been implicated in the progression of disease following coronary bypass surgery in men with moderate hypercholesterolemia. The association between lipid levels and restenosis following successful angioplasty is unclear in that data from different studies have been conflicting. The BARI study offers a unique opportunity to assess the effect of plasma lipoproteins and apoproteins on the progression and regression of coronary disease in a population undergoing serial angiographic follow-up at one and five years after revascularization. The hypotheses that total plasma cholesterol > 200mg/dl and low density lipoprotein cholesterol > 130mg/dl (levels determined by the expert panel of the National Cholesterol Education Program to require treatment) are associated with an increase in overall progression of coronary disease and increase the risk of restenosis following angioplasty can be tested. Although the "ideal" study would involve double randomization to lipid lowering therapy, in the climate of an increasing awareness and treatment of mild cholesterol abnormalities, important data has been collected. This sub-study of the BARI trial was reactivated 12/1/95-11/31/96 when the last group of our five year follow-up patients were admitted to the GCRC. This final group of 22 study participants were originally enrolled in the Lipid Study in 1994 at their three year follow up visit. Individuals were asked to continue in the Lipid Study so that more data will be available for comparison in the final analysis of this project. This portion of the BARI study was completed in December 1996. Currently this data is undergoing analysis which will dictate future plans for the presentation of this important data.